Author: Troy Theodosiou

Metabolism: Converting food into energy

Metabolism is the process by which your body converts what you eat and drink into energy. During this complex biochemical process, calories in food and beverages are combined with oxygen to release the energy your body needs to function.

To understand metabolic adaptation, it is first important to understand Total Daily Energy Expenditure (TDEE) and all of the components that comprise it. TDEE is the total amount of calories that you burn in a day and is comprised of four different processes: Basal Metabolic Rate (BMR), Non-Exercise Adaptive Thermogenesis (NEAT), Thermic Effect of Food (TEF), and Exercise Activity (EA). BMR accounts for ~60% of the TDEE and is the number of calories it takes for your body to carry out regular biological functions such as maintaining body temperature and organ function during rest. NEAT can be defined as all the smaller movements you make throughout the day that aren’t necessarily conscious exercise, but that requires energy such as fidgeting or yawning. TEF comprises ~10-15% of TDEE and is the amount of energy required to breakdown a specific macronutrient. For example, protein has a rather high TEF meaning to get your full caloric return, you have to invest a bit more energy to metabolize 1g of protein than 1g of carbs. Lastly, EA is the number of calories burned through exercise.

Although metabolism is linked to weight, slow metabolism is rarely the cause of excess weight gain. Although your metabolism influences your body’s basic energy needs, how much you eat and drink along with how much physical activity you get are the things that ultimately determine your weight.

Several factors determine your individual basal metabolism, including:

  • Your body size and composition. People who are larger or have more muscle burn more calories, even at rest.
  • Your sex. Men usually have less body fat and more muscle than do women of the same age and weight, which means men burn more calories.
  • Your age. As you get older, the amount of muscle tends to decrease and fat accounts for more of your weight, slowing down calorie burning.

Metabolism and weight

While it may be tempting to blame your metabolism on weight gain, metabolism is a natural process. Your body has many mechanisms that regulate it to meet your individual needs. Only in rare cases do you get excessive weight gain from a medical problem that slows metabolism, such as Cushing’s syndrome or having an underactive thyroid gland (hypothyroidism)

Weight gain is a complicated process. It’s likely a combination of genetic makeup, hormonal controls, diet composition and the impact of the environment on your lifestyle, including sleep, physical activity and stress.

All of these factors result in an imbalance in the energy equation. You gain weight when you eat more calories than you burn — or burn fewer calories than you eat.

While you don’t have much control over the speed of your basal metabolism, you can control how many calories you burn through your level of physical activity. The more active you are, the more calories you will burn!